A color image sensor is a necessary component in many optoelectronic devices. The color image sensor is a photoelectric conversion device that may transform detected light into electrical signals. A conventional image sensor may include a plurality of unit pixels arranged in an array on a semiconductor substrate. Each of the unit pixels may include a photodiode and/or a plurality of transistors. The photodiode may detect external light and/or may generate and store charges, and the transistor may output electrical signals according to the stored charges. A complementary metal oxide semiconductor (CMOS) image sensor is the most commonly used image sensor. The CMOS image sensor may include a photodiode that can receive and/or store optical signals and can realize images with signal processing. The photodiode may be manufactured in a single chip together with the signal processing device using COMS manufacturing techniques.
A time-of-flight (hereinafter referred to as ToF) camera is a range-imaging camera system that resolves distance based on the known speed of light, measuring the time-of-flight of a light signal between the camera and the subject for each point of the image. By integrating the image sensor and the ToF camera, the color image may sense depth information, and therefore a three-dimensional image-sensing apparatus may be realized.
In general, the ToF camera may also include a photodiode for detecting external light, and the photodiode of the ToF camera may have an absorption wavelength region different from that of the photodiode of the color image sensor. Therefore, a suitable optical filter is needed to filter undesired wavelength regions of the ToF camera and the color image sensor when they are integrated together. For example, in an ideal condition, only visible light can pass to the RGB pixel and only the infrared light can pass to the ToF pixel, so as to have minimum interference and noise. However, there is currently no suitable optical filter that can meet the above requirements. The optical filter is usually formed with depositing techniques in mass production. The unit pixels of an color image sensor and ToF camera are small, in large quantities, and in an alternate arrangement. Thus, there is no suitable and effective material or method for forming a two-band pass filter array which can be fabricated in mass production that permits only the light in the visible light range to pass to each unit pixel of the color image sensor and only the light in the infrared range to pass to each unit pixel of the ToF camera.
Accordingly, a suitable optical filter array and an image-sensing apparatus using same are needed.